Conventionally, an image processing apparatus which comprises an image data compression device for compressing image data read from an image input device, and a data storage device for storing image data compressed by the image data compression device, is known.
In an image processing apparatus that compresses an image by variable length coding of these image processing apparatuses, when the size of image data transmitted from an image data compression device has exceeded the storage capacity of a data storage device that stores image data, the image input process must be redone, and an image must be compressed again at a compression ratio higher than the previous one. Alternatively, the data size of image data transmitted from the image data compression device is counted, and when the transmitted image data size has exceeded a predetermined value, transmission of image property information is stopped to prevent the data size from exceeding the storage capacity of the data storage device, thus avoiding a re-input process of image data. However, if transmission of image property information is stopped, since the image property information is not available, an image process inside the image processing apparatus or an image correction process upon printing cannot be optimally made, and a desired image processing result cannot often be obtained.
For this reason, a conventional image processing system which compensates for omitted image property information by adding substitute information as header information upon transferring image data is known.
However, by merely adding substitute information (image property information) upon compressing image data, since substitute information is determined for each data transfer unit of the image data compression device, the substitute information is switched within a page from the beginning of new transfer of image data upon outputting image data, resulting in image quality deterioration. Also, some users cannot often determine on one of substitute information values to be set depending on their favors.
In the conventional image processing system, upon printing image data or transferring image data via a network, image data and image property information (attribute information indicating regions (e.g., a text region, photo region, and the like) to which pixels that form an image belong) are transferred after they are compressed. This is to improve the performance of the system as a whole by reducing the data size of data to be transferred.
However, there is no guarantee that the compression result of image data has a smaller data size than that before compression, and some image data may have a larger size than that before compression, thus lowering the performance of the overall system. For this reason, an image processing system, which accumulates the image data size before compression, and ceases to add image property information to transfer data when the compressed data size has reached a threshold value that influences the performance of the whole system, has been proposed.
Also, a conventional technique which compresses an image for respective tiles in a compression process has been proposed (e.g., refer to patent reference 1 (Japanese Patent Laid-Open No. 2003-69831)).
However, with the aforementioned conventional technique, upon executing an image process or the like by expanding image data with a poor compression ratio (compressed image data which has a larger data size than that before compression) again, since the image property information has been lost, a high-quality process that exploits the image property information cannot be done.
Furthermore, a conventional image processing apparatus which compresses an image comprises an image data compression unit for compressing image data read from an image input unit, and a data storage unit for storing image data compressed by the image data compression unit.
However, in this prior art, when the size of compressed image data which has been compressed by the image data compression unit and is to be stored in the data storage unit has exceeded the memory size of the data storage unit, the image must be re-input to the image input unit, compression parameters that can compress the image at a higher compression ratio than the previous one must be re-set in the image data comparison unit, and the re-input image data must be compressed again using the re-set compression parameters.
In addition, for example, the image data compression unit counts the size (data size) of compressed image data, and when the count value has exceeded a predetermined size, transmission of image property information is stopped to prevent the size of image data to be stored in the data storage unit from exceeding the memory size of the data storage unit, thus avoiding a re-input process of image data. In this case, since image property information (attribute information indicating regions (e.g., a text region, photo region, and the like) to which pixels that form an image belong) is omitted from the middle of data, an image process inside the apparatus or an image correction process upon printing cannot be optimally made, and a desired image processing result cannot often be obtained.